Survey (NHANES) III study, waist circumference explained obesity-related health risk significantly better than BMI when metabolic syndrome was taken as an outcome measure.Body fat measurement:An alternative way to determine obesity is to assess percent body fat. Doctors and scientists generally agree that men with more than 25% body fat and women with more than 30% body fat are obese. However, it is difficult to measure body fat precisely. The most accepted method has been to weigh a person underwater, but underwater weighing is a procedure limited to laboratories with special equipment. Two simpler methods for measuring body fat are the skinfold test, in which a pinch of skin is precisely measured to determine the thickness of the subcutaneous fat layer; or bioelectrical impedance analysis, usually only carried out at specialist clinics.

Their routine use is discouraged.Other measurements of body fat include computed tomography (CT/CAT scan), magnetic resonance imaging (MRI/NMR), and dual energy X-ray absorptiometry (DXA).Risk factors and comorbidities:The presence of risk factors and diseases associated with obesity are also used to establish a clinical diagnosis. Coronary heart disease, type 2 diabetes, and sleep apnea are possible life-threatening risk factors that would indicate clinical treatment of obesity. Smoking, hypertension, age and family history are other risk factors that may indicate treatment.Effects on health:A large number of medical conditions have been associated with obesity. Health consequences are categorised as being the result of either increased fat mass (osteoarthritis, obstructive sleep apnea, social stigma) or increased number of fat cells (diabetes, cancer, cardiovascular disease, non-alcoholic fatty liver disease). Mortality is increased in obesity, with a BMI of over 32 being associated with a doubled risk of death.

There are alterations in the body's response to insulin (insulin resistance), a proinflammatory state and an increased tendency to thrombosis (prothrombotic state).Disease associations may be dependent or independent of the distribution of adipose tissue. Central obesity (male-type or waist-predominant obesity, characterised by a high waist-hip ratio), is an important risk factor for the metabolic syndrome, the clustering of a number of diseases and risk factors that heavily predispose for cardiovascular disease. These are diabetes mellitus type 2, high blood pressure, high blood cholesterol, and triglyceride levels (combined hyperlipidemia).Apart from the metabolic syndrome, obesity is also correlated with a variety of other complications. For some of these complaints, it has not been clearly established to what extent they are caused directly by obesity itself, or have some other cause (such as limited exercise) that causes obesity as well.Cardiovascular: congestive heart failure, enlarged heart and its associated arrhythmias and dizziness, varicose veins, and pulmonary embolism Endocrine: polycystic ovarian syndrome (PCOS), menstrual disorders, and infertility Gastrointestinal: gastroesophageal reflux disease (GERD), fatty liver disease, cholelithiasis (gallstones), hernia, and colorectal cancer Renal and genitourinary: erectile dysfunction, urinary incontinence, chronic renal failure, hypogonadism (male), breast cancer (female), uterine cancer (female), stillbirth Integument (skin and appendages): stretch marks, acanthosis nigricans, lymphedema, cellulitis, carbuncles, intertrigo Musculoskeletal: hyperuricemia (which predisposes to gout), immobility, osteoarthritis, low back pain Neurologic: stroke, meralgia paresthetica, headache, carpal tunnel syndrome, dementia, idiopathic intracranial hypertension Respiratory: obstructive sleep apnea, obesity hypoventilation syndrome, asthma Psychological: Depression, low self esteem, body.

Obesity

Obesity is a condition in which the natural energy reserve, stored in the fatty tissue of humans and other mammals, exceeds healthy limits. It is commonly defined as a body mass index (weight divided by height squared) of 30 kg/m2 or higher.Although obesity is an individual clinical condition, some authorities view it as a serious and growing public health problem. Some studies show that excessive body weight has been shown to predispose to various diseases, particularly cardiovascular diseases, diabetes mellitus type 2, sleep apnea and osteoarthritis. Classification:Obesity can be defined in absolute or relative terms. In practical settings, obesity is typically evaluated in absolute terms by measuring BMI (body mass index), but also in terms of its distribution through waist circumference or waist-hip circumference ratio measurements. In addition, the presence of obesity needs to be regarded in the context of other risk factors and comorbidities (other medical conditions that could influence risk of complications).

BMI:BMI, or body mass index, is a simple and widely used method for estimating body fat. BMI was developed by the Belgian statistician and anthropometrist Adolphe Quetelet. It is calculated by dividing the subject's weight by the square of his/her height, typically expressed either in metric or US "Customary" units:Metric: BMI = kg / m2 Where kg is the subject's weight in kilograms and m is the subject's height in metres.US/Customary: BMI = lb * 703 / in2 Where lb is the subject's weight in pounds and in is the subject's height in inches.The most commonly used definitions, established by the WHO in 1997 and published in 2000, provide the following values:A BMI less than 18.5 is underweight A BMI of 18.5–24.9 is normal weight A BMI of 25.0–29.9 is overweight A BMI of 30.0–39.9 is obese A BMI of 40.0 or higher is severely (or morbidly) obese A BMI of 35.0 or higher in the presence of at least one other significant comorbidity is also classified by some bodies as morbid obesity.

In a clinical setting, physicians take into account race, ethnicity, lean mass (muscularity), age, sex, and other factors which can affect the interpretation of BMI. BMI overestimates body fat in persons who are very muscular, and it can underestimate body fat in persons who have lost body mass (e.g. many elderly). Mild obesity as defined by BMI alone is not a cardiac risk factor, and hence BMI cannot be used as a sole clinical and epidemiological predictor of cardiovascular health.Waist circumference:BMI does not take into account differing ratios of adipose to lean tissue; nor does it distinguish between differing forms of adiposity, some of which may correlate more closely with cardiovascular risk. Increasing understanding of the biology of different forms of adipose tissue has shown that visceral fat or central obesity (male-type or apple-type obesity, also known as "belly fat") has a much stronger correlation, particularly with cardiovascular disease, than the BMI alone.

The absolute waist circumference (>102 cm in men and >88 cm in women) or waist-hip ratio (>0.9 for men and >0.85 for women) are both used as measures of central obesity.In a cohort of almost 15,000 subjects from the National Health and Nutrition Examination